The present invention relates to the fabrication of integrated circuits. More particularly, the invention provides a technique, including a method and apparatus, for cleaning interior surfaces of a chemical vapor deposition (CVD) treatment chamber. The present invention also may be applied to an apparatus for plasma etching, physical vapor deposition (PVD), and the like.
In the manufacture of high density integrated circuits, commonly termed VLSI devices, contaminant particles are a major problem. In particular, contaminant particles attach themselves to unpassivated elements of integrated circuit devices during fabrication, where they can create short circuits or cause reliability problems. Therefore, the contaminant particles ultimately reduce the yield of good dies on a conventional semiconductor wafer. Even worse, as feature sizes decrease, the influence of contaminant particles in the fabrication of integrated circuits becomes greater.
Accordingly, semiconductor equipment vendors and users, alike, often rely upon elaborate and expensive techniques to control potential sources of contaminant particles. Such techniques include the use of ultra-clean rooms, super automated handling equipment, and sophisticated process controls during the fabrication of integrated circuits to reduce the potential sources of contaminant particles. However, such techniques can only be of limited success because substantial amounts of contaminant particles in integrated circuit fabrication are actually derived from reactant by-products created when semiconductor wafers undergo processing.
These reactant by-products often attach themselves to interior surfaces of a process chamber and form into a "thick" contaminant residue layer. Typically, the contaminant residue layer is derived from by-products from reactant gases and other by-products already attached to interior surfaces of the process chamber. Portions of the contaminant residue layer can flake off and deposit onto unpassivated surfaces of the integrated circuit, thereby damaging such integrated circuit by causing short circuits, broken connections, missing elements, and reliability problems.
In a conventional silicon dioxide deposition process, for example, the reactant gases used are predominately mixtures of organic silane and ozone. These gases are introduced into the chamber to form a silicon dioxide layer on surfaces of a semiconductor water. As the silicon dioxide layer is formed, however, these gases also form particulate compositions. The particulate compositions form loosely attached contaminant residues on the interior surfaces of the process chamber. These interior surfaces of the chamber include a dispersion head, electrodes, walls, and any other exposed surfaces. The loosely attached contaminant residues often form into a thicker contaminant residue layer, which is likely to flake off and fall onto the integrated circuit.
To prevent portions of the contaminant residue layer from damaging the integrated circuit, a variety of cleaning techniques have been proposed. These cleaning techniques require separate process steps, which include machine shut-down and cleaning, after each deposition step. This is time consuming, expensive, and difficult to achieve. Of course, when the system is not operating, its throughput drops, rendering the manufacturing process all the more expensive.
An example of a conventional cleaning technique for a silicon dioxide deposition apparatus involves sequential steps of machine shut-down, dismantling portions of the process chamber, and hand wiping interior surfaces of the process chamber using appropriate materials, e.g. rinse water and clean wipes. The hand wiping step attempts to remove contaminant residues from the interior surfaces. Other conventional cleaning techniques sometimes used rely upon hand wiping the interior surfaces of the process chamber with a liquid chemical solution, such as a dilute hydrofluoric acid solution, or an organic solvent, in an attempt to dissolve and remove the contaminant residues. These conventional cleaning techniques also are applied to vacuum exhaust channels and pump systems because diminished vacuum or suffocation often occurs with accumulated residues or contaminant clogging. The conventional techniques are time consuming, and generally provide additional sources for even more contamination.
Plasma enhanced dry cleaning techniques have also been used to remove contaminant residues from interior surfaces of a deposition chamber. The dry cleaning techniques often take place during a separate process step, for example, by introducing cleaning gases into a process chamber, striking a plasma from the cleaning gases, and using the plasma to remove contaminant residues. Preferably, ionic species in the plasma combine with the contaminant residues to form volatile products which are removed from the process chamber. The dry cleaning techniques typically must be used after every deposition run to be effective in keeping the interior surfaces of the process chamber substantially free from contaminant residues. Accordingly, the dry cleaning techniques consume valuable production time, and decrease machine availability or machine up-time. The use of dry cleaning techniques every deposition run also consumes cleaning gases, which can be expensive and difficult to obtain. Further, dry cleaning techniques often remove portions of the actual chamber surfaces by an etching reaction.
From the above, it can be seen that a technique for removing contaminant particles from a process chamber which reduces the amount of machine downtime would be desirable.